Rate of Expansion of Universe is not decreasing, but increasing due to Dark Energy!

It had always been assumed that the matter of the Universe would slow its rate of expansion. Mass creates gravity, gravity creates pull, the pulling must slow the expansion. But supernovae observations showed that the expansion of the Universe, rather than slowing, is accelerating. Something, not like matter and not like ordinary energy, is pushing the galaxies apart. This “stuff” has been dubbed dark energy, but to give it a name is not to understand it. Whether dark energy is a type of dynamical fluid, heretofore unknown to physics, or whether it is a property of the vacuum of empty space, or whether it is some modification to general relativity is not yet known.

Question of Equilibrium : Answer in Inflationary model

Our investigation shows that the early Universe was too homogeneous. How could pieces of the Universe that had never been in contact with each other have come to equilibrium at the very same temperature? This and other cosmological problems could be solved, however, if there had been a very short period immediately after the Big Bang where the Universe experienced an incredible burst of expansion called “inflation.” For this inflation to have taken place, the Universe at the time of the Big Bang must have been filled with an unstable form of energy whose nature is not yet known. Whatever its nature, the inflationary model predicts that this primordial energy would have been unevenly distributed in space due to a kind of quantum noise that arose when the Universe was extremely small. This pattern would have been transferred to the matter of the Universe and would show up in the photons that began streaming away freely at the moment of recombination.

Proofs of Big Bang

1. Expanding galaxies: Hubble in 1929, noted that galaxies outside our own Milky Way were all moving away from us, each at a speed proportional to its distance from us. He quickly realized what this meant that there must have been an instant in time (now known to be about 14 billion years ago) when the entire Universe was contained in a single point in space. The Universe must have been born in this single violent event which came to be known as the “Big Bang.”

2. Cosmic Background radiation: Those early photons – the afterglow of the Big Bang known as cosmic background radiation – can be observed today.

Missions to study Big Bang

1. Cosmic Background Explorer (COBE) : NASA has launched two missions to study the cosmic background radiation, taking “baby pictures” of the Universe only 400,000 years after it was born. The first of these was the Cosmic Background Explorer (COBE).

2. Wilkinson Microware Anisotropy Probe (WMAP): The second mission to examine the cosmic background radiation was the Wilkinson Microware Anisotropy Probe (WMAP). With greatly improved resolution compared to COBE, WMAP surveyed the entire sky, measuring temperature differences of the microwave radiation that is nearly uniformly distributed across the Universe. The picture shows a map of the sky, with hot regions in red and cooler regions in blue. By combining this evidence with theoretical models of the Universe, scientists have concluded that the Universe is “flat,” meaning that, on cosmological scales, the geometry of space satisfies the rules of Euclidean geometry (e.g., parallel lines never meet, the ratio of circle circumference to diameter is pi, etc).

3. Planck: A third mission, Planck, led by the European Space Agency with significant participation from NASA, was launched in 2009.  Planck is making the most accurate maps of the microwave background radiation yet. With instruments sensitive to temperature variations of a few millionths of a degree, and mapping the full sky over 9 wavelength bands, it measures the fluctuations of the temperature of the CMB with an accuracy set by fundamental astrophysical limits.

Telescopes: Today NASA spacecraft such as the Hubble Space Telescope and the Spitzer Space Telescope continue Edwin Hubble’s work of measuring the expansion of the Universe.

The Big Bang Theory in Laymen Language

Universe is flat!

In the beginning there was only energy. This energy got converted to small particles (like photons). As there were earlier free electrons too, these earlier photons got scattered by first electrons. The result: a dark universe! But later, when electrons combined with protons and neutrons (atomic nuclei), atoms were formed. As then there were no free electrons to scatter photons then the Universe became transparent!

Some unknown energy kept particles pushing apart. Meanwhile the universe started too cool too. Atoms like Hydrogen were formed. Atoms formed molecules, molecules combined to form compounds and so on. The final result : all the big objects like what we see today planets, stars, galaxies and so on! But now when we analyse the universe, the shape of the universe is flat, ie as if explosion taken place on a 2 -dimensional table!

The two theories which formed the basis of the big bang theory are : (1) Einstein’s General Theory of Relativity and (2) The Cosmological Principles, which states that the universe is homogeneous through out. Hope at least the basics of the ‘not-so-easy-to-understand’ Big Bang theory of energy to mass conversion is clear! If not, have a look at 2-3 reference documents.

1. Timeline of the Big Bang.

2. Shape of the universe.

3. Beyond Big Bang Cosmology.